1 . Field of the Invention
The present invention relates to an ink tank for recording devices, and more specifically to an ink tank composed of improved composition materials.
2. Description of the Prior Art/Related Art
Molding a container that stores liquids from polymeric materials have been applied to various technical fields.
For instance, in Japanese Patent Application Laying-open No. 8-217924 (1996), as materials to be used in film, sheet, and various molded products, polyolefin resins such as polyethylene and polypropylene are described. To these resins, various additives are added to aim at improved characteristics. In the above-mentioned publication, from the standpoint of improving processing stability and transparency, the addition of organic phosphide compounds, sorbitol compounds, and aluminum compounds at prescribed ratios to the polyolefin resins is proposed, and it has been disclosed that they are excellent materials for improving processing stability and transparency.
Furthermore, in Japanese Patent Application Laying-open No. 10-114842 (1998), a material comprising propylene polymer to which specific siloxane, sorbitol based materials, and a neutralizing agent selected from the group consisting of metal soap, hydrotalcite, aluminum silicate, zinc oxide, calcium oxide and hydroxides of Group II metals are added is proposed as a material that composes syringe barrel, plunger, tube material, and tube assemblages which require sterilization with high energy radiation. It is disclosed that the material has brittleness resistance, transparency and injection moldability.
Ink tanks for recording devices, in particular, ink tanks which store ink for ink jet recording units, are also composed of resins. As materials used for such ink tanks, a material which meets the following requirements is desired.
A material
1. which has ink resistance so that it is not dissolved by the stored ink; PA1 2. which does not elute in the ink a part of the components of the ink tank compositional material which affects the performance of the ink; PA1 3. which has barrier properties against the ink components so that the composition or the composition ratio of the ink do not change; PA1 4. which possess sufficient strength to withstand the impact when the tank is dropped during handling; PA1 5. of which the cost and the processing cost shall be moderate, since it is a supplied product; and PA1 6. which is capable of recycling, as the consciousness towards global environmental problems have recently heightened.
Furthermore, although it depends upon the required performance for the ink jet-recording unit, there are cases in which it is necessary to have a degree of transparency where the remainder of ink inside of the tank can be optically detected.
As a material that satisfies all of the above-mentioned requirements, for instance, resins such as modified polyphenylene oxide (modified PPO: trade name: NORYL), polystyrene (PS), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polypropylene (PP), and polysulfone (PSF) have been used. In particular, in recent years, desire has heightened for materials that are recyclable and transparent, and polypropylene type resins or polyethylene type resins have been used.
However, the following phenomena were confirmed for ink tanks for which polypropylene type resins (hereinafter referred to as PP) or polyethylene type resins (hereinafter referred to as PE) were used as raw materials.
Materials having high crystallinity such as PP, PE, in particular, PP provides molded articles of which the crystallinity is not uniform, in general, and scatters the light, so the transparency of the molded article is often insufficient. In order to prevent the molded article from becoming opaque, nucleating agents are added to the material as additives. That is, the addition of a proper nucleating agent results in making the molded article into uniform and fine crystals to improve the rigidity and thermal deflection temperature of PP, as well as improving its transparency.
As such nucleating agents for PP, bis(p-methyl benzylidene)sorbitol (trade name: Gelall MD: Shin-Nihon Rika K.K.) is generally used. However, it has been found that bis(p-methyl benzylidene)sorbitol is easily eluted in ink used for the ink jet recording device. Depending on the environmental conditions, the eluted substances are sometimes deposited. And even though infrequently, the eluted substances are deposited on the ink flow channel, filter, or ink nozzle of the printer, thereby affecting the flow of the ink, and as a result, the printing.
In addition, neutralization agents are used in polyolefins such as PP and PE to prevent the influence of residues formed by the catalysts used at the time of polymerization. As neutralization agents, metal salts of fatty acids such as calcium stearate are generally used. It was found that such agents are easily eluted as well, in ink used for the ink-jet recording device. Depending on the environmental conditions, the eluted substances are sometimes deposited. And similar to the case of the nucleating agent, even though infrequently, the eluted substances are deposited on the ink flow channel, filter, or ink nozzle, thereby affecting the flow of the ink, and as a result, the printing.
Even in case of the materials described in the aforementioned patent publications, for instance, the organic phosphide compounds disclosed in Japanese Patent Application Laying-open No. 8-217924, and the siloxane disclosed in Japanese Patent Application Laying-open No. 10-114842, there is a possibility of eluting them in the ink. Even in case of the materials disclosed as being outstanding in stability and transparency, or the materials having brittleness resistance, transparency and injection moldability, they are not necessarily adequate as compositional materials for ink tanks.
As mentioned above, the depositions in the ink channel, filter, or ink nozzle, are normally discharged by cleaning operation (recovery operations such as suction, pressurization, etc.) of the recording device, and contrivance was made so that depositions would not affect the printing.
However, particularly in recent years, as the liquid droplets discharged from the ink-jet printer became smaller, trace of depositions which could no longer be removed sufficiently from the highly precise fine nozzles by the common recovery operation could cause ink flow to be disturbed. And the influence can no longer be neglected.